Fan stop



10, 1939. A. A. FRINK 7 4 ,3

FAN STOP Filed Nov. 18, 1956 INVENTOR Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE FAN STOP Application November 18, 1936, Serial No. 111,425

3 Claims.

This invention relates to a stop or holdback for fan shafts and the like for preventing rotation thereof in the reverse direction when power is shut off or interrupted.

The invention is of particular importance in conjunction with baghouse fans and the like which are periodically shut down to permit removal of material collected by the bags. When this occurs the reverse air current through the fan tends to cause the fan to drift in the reverse direction. Upon application of power for starting up the fan, it is then necessary to overcome the reverse momentum and bring the fan to rest before starting its normal rotation. This results in the waste of a substantial amount of power and also produces a torque which may damage the motor, starting box mechanism, bearings, etc.

The present invention overcomes the above difficulties by providing a novel stop which engages a ratchet on the fan shaft when the fan comes to rest and locks the same against movement in the reverse direction. A means is also provided to hold the stop disengaged when the fan is operating normally.

The invention also consists in the various details of construction and combinations of parts hereinafter more fully set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be more particularly pointed out in the claims appended hereto, the broader aspects of the invention will be better understood by referring to the following description, taken in connection with the accompanying drawing, in which one embodiment thereof has been set forth for purposes of illustration.

In the drawing:

Fig. 1 is a side elevation of a fan, shaft and associated mechanism illustrating one embodiment of the present invention;

Fig. 2 is a section taken on the line 2-2 of Fig. 1;

Fig. 3 is a detail view of the ratchet wheel forming part of the stop mechanism;

Fig. 4 is a section taken along the line 4--4 of Fig. 3;

Fig. 5 is a detail view of a modified form of ratchet wheel; and

Fig. 6 is a section taken along the line 6-6 of Fig. 5.

Referring to the drawing more in detail, the invention is shown as applied to a shaft l0 which is mounted in suitable bearings in a pair of housings ll supported on a base l2. The shaft l0 drives a fan 14 mounted in a housing l5 and adapted to draw air from a duct 16 and to discharge the same into a duct IT. The fan l4 and ducts I6 and I! may be of the type commonly employed in connection with a bag-house or the like for use in removing suspended particles from gases. It is to be understood that any suitable type of fan may be employed and that the invention is particularly applicable to a fan which is capable of reversing in response to a reverse draft through the ducts I6 and H, such as may occur when the fan is shut down. These ducts constitute a flue.

The stop mechanism, in accordance with the present invention, comprises a ratchet wheel 20 which is shown in Figs. 3 and 4 as formed of wood in two sections which are held together by bolts 2| and is clamped about the shaft Ill. The ratchet wheel 20 is provided with a plurality of teeth 22 which are engaged by a pawl 23 to prevent rotation of the wheel in one direction. for example, in a clockwise direction while permitting free rotation thereof in the opposite direction. The pawl 23 is mounted by a hinge 24 on a bracket 25 which is supported on the base 12 by a bolt 26. The bracket 25 and pawl 23 are positioned on an incline so that the pawl is held by gravity against the teeth 22. The hinge 24 may include a stop (not shown) to prevent the pawl from being raised past the vertical position.

In order to release the pawl when the shaft I0 is operating normally, a plurality of vanes 30 are provided. These vanes 30 may comprise metal strips which are passed through suitable slots 3| in the ratchet wheel 20 and extend on opposite sides thereof a distance adapted to produce an air current for the purpose to be described. A wing 32 is mounted on the pawl 23 and is held by a spring clip 33 thereon. This wing 32 extends on opposite sides of the pawl 23 into a position to intercept the air current produced by the vanes 30 when the shaft 10 is rotated. The air current thus produced causes the pawl 23 to be disengaged from the teeth 22 when the shaft 10 is rotating at normal speed. When the shaft comes to rest, however, the air current is interrupted thereby permitting the pawl 23 to fall against the ratchet wheel 20 and to securely lock the same and the shaft [0 against reverse rotation. A shield 34 may be mounted on the base l2 in front of the ratchet wheel 2|] for safety purposes. This shield is preferably of open construction so as not to interfere with the production of an air current by the vanes 30.

While the ratchet wheel 20 has been shown and described as formed of wood, it is obvious that wheel 40 is similar in construction to the ratchet, wheel 20 above described. It is provided, how -,1

ever, with a plurality of slots 4| arranged at the periphery thereof. A set of VanesAZ of flexible material, such as rubber ormthe like are held, in.

these slots 4!. The operation ofithis-embodiment is similar to that above described. Theflexible vanes 42, however, reduce the possibility of injury by the device and produce a smooth and. uniform] operation.

It is evident that the vanes and wheels may bemade of any suitable materials and may be assembled in any convenient manner. Although alparticularembodiment of the inventionhas been shownand described rfor purposes of illustration, various changes and modifications may bemadeby thoseskilled in the,art within the sc ope of the invention.

What is claimed is:

1, In combination, a fan having a drive shaft,

stop mechanism for preventing reverse rotation thereof v comprising a toothed member mounted on said shaft, a pawl mounted to engage said member to lock the same against reverse rotation, vanes mounted on said toothed member to produce a current of air when said member is rotating normally and means associated with said pawl and actuated in response to said current of air to hold said pawl out of engagement with said toothed member.

2.= In combination, a fanhaving adrive shaft, stop mechanism for preventing reverse rotation thereof comprising a toothed member mounted onnsaid shaft, a pawl mounted to engage said member to lock the same against reverse rotation, vanes extending on opposite sides of said toqthed member to produce a current of air when saidemembervis,operating normally and wings mountedfonsaid pawl and responsive to said ourrent of air ito hold-said pawl out of engagement with said toothed member.

3.;Thecombination comprising a flue, a drive shaft having a fan and a ratchet wheel mounted h reon, saidvfan ei e mo nt i er ally of i ea idisa d r 'chetiwh e ein .m u te i x err nallythereof a 'pawl adapted toieng'a'ge said a het whe l nd-p rmit c et np Sai Sh me .d tibnf nl l eags, qn ia f te: tion ,of th e shaij t :in that direction producinga current of air, and j means associated with said aw n ercebt na.saidl' i urr t su c L d ire j i awl y r; n a enien th. i

tche wh l. 39d ,ma llfieifi 19 di a m nt hilasaid ,shai woman; ota ng-g le-E3131. A} RIliKr; 

